Plant Biotechnology - General Botany - Lecture Slides, Slides of Botany and Agronomy

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Plant Biotechnology and GMOs

Chapter 14

(Plus other bits and bobs)

Plant Biotechnology

• “For centuries, humankind has made improvements to crop

plants through selective breeding and hybridization — the

controlled pollination of plants.

• Plant biotechnology is an extension of this traditional plant

breeding with one very important difference —

• plant biotechnology allows for the transfer of a greater variety of genetic information in a more precise, controlled manner.”

Figure 11.

Increasing crop yields

• Algal blooms - a relatively rapid increase in the population of (usually) phytoplankton algae in an aquatic system.
• Causes the death of fish and disruption to the whole ecosystem of the lake.
• International regulations has led to a reduction in the occurrences of these blooms.

Figure 11.

Chemical pest control

• Each year, 30% of crops are lost to insects and other crop pests.
• The insects leave larva, which damage the plants further.
• Fungi damage or kill a further 25% of crop plants each year.
• Any substance that kills organisms that we consider undesirable are known as a pesticide.
• An ideal pesticide would:-
  • Kill only the target species
  • Have no effect on the non- target species
  • Avoid the development of resistance
  • Breakdown to harmless compounds after a short time Docsity.com

Figure 11.

Chemical pest control

• DDT persists in the food chain.
• It concentrates in fish and fish- eating birds.
• Interfere with calcium metabolism, causing a thinning in the eggs laid by the birds – break before incubation is finished – decrease in population.
• Although DDT is now banned, it is still used in some parts of the world.

Plant Biotechnology

• The use of living cells to make products such as

pharmaceuticals, foods, and beverages

• The use of organisms such as bacteria to protect

the environment

• The use of DNA science for the production of

products, diagnostics, and research

Why would we want to modify an

organism?

• Better crop yield, especially under harsh conditions.
• Herbicide or disease resistance
• Nutrition or pharmaceuticals, vaccine delivery
• “In 2010, approximately 89% of soy and 69% of corn

grown in the U.S. were grown from Roundup Ready®

seed.”

http://www.oercommons.org/courses/detecting-genetically-modified-food-by-pcr/

Roundup Ready Gene

• The glyphosate resistance gene protects food plants against

the broad-spectrum herbicide Glyphosate - N-

(phosphonomethyl) glycine [Roundup®], which efficiently

kills invasive weeds in the field.

• The major advantages of the "Roundup Ready®” system

include better weed control, reduction of crop injury,

higher yield, and lower environmental impact than

traditional weed control systems.

• Notably, fields treated with Roundup® require less tilling;

this preserves soil fertility by lessening soil run-off and

oxidation.”

Glyphosate - N-(phosphonomethyl) glycine

• It does this by inhibiting the enzyme 5- enolpyruvylshikimate-3-phosphate synthase (EPSPS), which catalyzes the reaction of shikimate-3-phosphate (S3P) and phosphoenol pyruvate to form 5- enolpyruvyl-shikimate-3-phosphate (ESP).
• ESP subsequently dephosphorylated to chorismate , an essential precursor in plants for these aromatic amino acids.

Glyphosate

Glycine

Roundup Ready Gene

• Glyphosate functions by occupying the binding site of the phosphoenol pyruvate , mimicking an intermediate state of the enzyme substrates complex.
• The "Roundup Ready®” system introduces a stable gene alteration which prevents Glyphosate binding and allowing the formation of the essential aromatic amino acids

Environmental degradation

• When glyphosate comes into contact with the soil, it can be rapidly bound to soil particles and be inactivated.
• Unbound glyphosate can be degraded by bacteria.
  • However, glyphosate has been shown to increase the infection rate of wheat by fusarium head blight in fields that have been treated with glyphosate.
• In soils, half-lives vary from as little as 3 days at a site in Texas to 141 days at a site in Iowa.
• In addition, the glyphosate metabolite amino methyl phosphonic acid has been shown to persist up to 2 years in Swedish forest soils.
• Glyphosate absorption varies depending on the kind of soil.

Insect Resistance

• B. thuringiensis (commonly known as 'Bt') is an insecticidal bacterium, marketed worldwide for control of many important plant pests - mainly caterpillars of the Lepidoptera (butterflies and moths) but also mosquito larvae, and simuliid blackflies that vector river blindness in Africa.
• Bt products represent about 1% of the total ‘agrochemical’ market (fungicides, herbicides and insecticides)

Genetically modified crops

• Need to build in a:

• Promoter

• Stop signal

PROMOTER INTRON CODING SEQUENCE poly A signal

ON/OFF Switch Makes Protein stop sign

Genetically modified crops

• So to modify a plant :
• Need to know the DNA sequence of the gene of interest
• Need to put an easily identifiable maker gene near or next to the gene of interest
• Have to insert both of these into the plant nuclear genome
• Good screen process to find successful insertion